Implantable Medical Devices Including Selectable Notch Filter Circuits
First Claim
1. A method of sensing cardiac activity of a patient with an implanted cardiac stimulus device having first and second implanted electrodes, the method comprising:
- receiving a cardiac signal captured using the first and second implanted electrodes;
digitizing the cardiac signal;
filtering the digitized cardiac signal using a digital filter defined by a first set of filter coefficients; and
analyzing the filtered digitized cardiac signal to detect cardiac events;
wherein the method further comprises a filter adaptation method comprising;
determining whether the set of filter coefficients corresponds to an ambient noise source present in the environment outside of the patient; and
, if not, selecting a second set of filter coefficients.
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Abstract
Described are selectable notch filter circuits comprising at least two different notch filter capabilities, each of which is capable of filtering interference of a designated fundamental frequency and a second harmonic of the designated fundamental frequency from an electrical signal. Each of the notch filters of the circuit is specific for real time filtering of a different designated fundamental frequency and a second harmonic thereof from digitized signal data input into the circuit. The filtering capability of each filter is dictated by control logic, which uses a coefficient set specific for the designated fundamental frequency and harmonics thereof. By using different coefficient sets, different designated fundamental frequencies and at least their second harmonic frequencies can be filtered from digitized signal data input into the circuit. Because the control logic can utilize at a given time any one (or, if desired, none) of the coefficient sets available to it, different interfering fundamental frequencies can be filtered, if and as necessary, from digitized input signal data collected over time at a substantially equivalent sampling rate. Also described are devices including one or more such selectable notch filter circuits, including implantable medical devices such as implantable cardioverter/defibrillators, as well as methods of using such devices.
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Citations
9 Claims
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1. A method of sensing cardiac activity of a patient with an implanted cardiac stimulus device having first and second implanted electrodes, the method comprising:
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receiving a cardiac signal captured using the first and second implanted electrodes;
digitizing the cardiac signal;
filtering the digitized cardiac signal using a digital filter defined by a first set of filter coefficients; and
analyzing the filtered digitized cardiac signal to detect cardiac events;
wherein the method further comprises a filter adaptation method comprising;
determining whether the set of filter coefficients corresponds to an ambient noise source present in the environment outside of the patient; and
,if not, selecting a second set of filter coefficients. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification
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- Resources
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Current AssigneeCameron Health Inc (Boston Scientific Corporation)
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Original AssigneeCameron Health Inc (Boston Scientific Corporation)
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InventorsOstroff, Alan, Phillips, James
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Application NumberUS11/965,961Publication NumberTime in Patent OfficeDaysField of SearchUS Class Current607/2CPC Class CodesA61N 1/37 Monitoring; ProtectingA61N 1/3718 Monitoring of or protection...H03H 17/0294 Variable filters; Programma...
